A Comparative Study between the Effectiveness of a Softer Grade Binder and a Rejuvenating Agent in Hot Mix Asphalt with Reclaimed Asphalt Pavement

Incorporation of RAP in HMA increases the stiffness of the mix because of the presence of highly aged binder in RAP and consequently escalates the potential of cracking susceptibility. Two options, either a softer grade binder or a rejuvenator can be introduced with RAP to obtain a desired performance grade of the binder. In this study, these two options were compared with respect to their performances. In one case, a softer PG 58-34 binder was blended with RAP binder with RAP-binder ratio of 0.356 and the high temperature binder grade was determined. In the other case, two commercially available rejuvenators were used and were blended with PG 67-34 binder. Percentages of rejuvenators were selected to achieve the same binder grade of the softer binder with RAP binder. Rheological and mechanical properties of unaged and laboratory aged blended binders were investigated by multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests and the results were compared with the properties of virgin PG 67-34 binder. Low-temperature cracking potential of RAP mixes were evaluated by semi-circular bending (SCB) test. It was observed that although both the softer binder with RAP binder and rejuvenated regular binder with RAP binder have the same high temperature grade, rejuvenators have more potential of improving low temperature grade and fatigue life. SCB test results show that the plant-based bio oil rejuvenator performs much better by showing higher fracture energy at low temperature.